What are the screening criteria for components? What are the filter items?

Date：2021-07-29 16:13:00 Views：3583

The screening requirements of component users are generally determined by the overall model unit. The secondary screening of components is a supplement to the primary screening. The service conditions and application environment of components shall be comprehensively considered on the basis of the items and stress of the primary screening. Due to different tasks undertaken by each unit and different requirements for product reliability, there is no unified screening standard.

Component screening classification:

Classification by nature:

(1) Examination and screening: microscopic examination, infrared non-destructive examination and X-ray non-destructive examination.

(2) Sealing screening: liquid immersion leak detection, helium mass spectrometry leak detection, radioactive tracer leak detection and humidity test.

(3) Environmental stress screening: vibration, shock, centrifugal acceleration, temperature shock, temperature storage and comprehensive stress.

(4) Life screening: power aging and reverse bias aging screening.

Classification by production process:

(1) Process screening of production line

(2) Finished product screening

(3) Assembly, adjustment and screening (i.e. simulating the service state of the whole machine)

Classification by filtering method:

(1) Distribution truncation screening: sorting the parameter performance of components;

(2) Stress intensity screening: measure and sort the components after applying a certain strength of stress;

(3) Aging screening: Test and screen the components after applying various stresses within the specified time;

(4) Linear discrimination screening: similar to aging screening, but it should be discriminated by mathematical statistics technology;

(5) Precision screening: carry out long-term aging under the conditions close to the use of components, and accurately measure the parameter change for many times for selection and prediction.

Common screening items of components:

High temperature storage

The failure of electronic components is mostly caused by various physical and chemical changes in their body and surface, which are closely related to temperature. After the temperature rises, the chemical reaction speed is greatly accelerated and the failure process is accelerated, so that the defective components can be exposed and removed in time.

High temperature screening is widely used in semiconductor devices. It can effectively eliminate devices with failure mechanisms such as surface contamination, poor bonding and oxide defects. Usually, the device needs to be stored at the maximum junction temperature for 24 ~ 168 hours.

High temperature screening is simple and inexpensive, and can be implemented on many components. After high-temperature storage, the parameter performance of components can be stabilized and the parameter drift in use can be reduced. The thermal stress and screening time of various components shall be properly selected to avoid new failure mechanism.

Power aging

When screening, under the combined action of thermoelectric stress, it can well expose a variety of potential defects in the body and surface of components. It is an important item of reliability screening.

Various electronic components are usually aged for several hours to 168 hours under rated power conditions. Some products, such as integrated circuits, can not change the conditions at will, but can adopt high-temperature working mode to improve the working junction temperature and achieve high stress state. The electrical stress of various components shall be properly selected, which can be equal to or slightly higher than the rated conditions, but can not lead to new failure mechanism.

The power aging needs special test equipment and its cost is high, so the screening time should not be too long. Civil products usually take several hours, military highly reliable products can choose 100 or 168 hours, and aerospace components can choose 240 hours or even longer.

Temperature cycle

Electronic products will encounter different ambient temperature conditions in the process of use. Under the stress of thermal expansion and cold contraction, components with poor thermal matching performance are easy to fail. Temperature cycle screening uses the thermal expansion and contraction stress between extreme high temperature and extreme low temperature, which can effectively eliminate the products with thermal performance defects. The common screening conditions for components are - 55 ℃ to + 125 ℃, with 5-10 cycles.

Centrifugal acceleration

Centrifugal acceleration test is also called constant stress acceleration test. This screening is usually carried out on semiconductor devices. The centrifugal force generated by high-speed rotation is applied to the devices to eliminate devices with too weak bonding strength, poor internal lead matching and poor mounting. Usually, the centrifugal acceleration of 20000g is selected and the test is continued for one minute.

Monitoring vibration and shock

It is often called monitoring vibration or monitoring impact test to monitor the electrical performance of products at the same time of vibration or impact test. This test can simulate the vibration and impact environment during the use of the product, effectively eliminate components with poor mechanical structure such as instantaneous short circuit and open circuit, and find faults such as false welding in the whole machine. Monitoring vibration and shock is an important screening item in highly reliable relays, connectors and military electronic equipment.

Typical vibration conditions: the frequency is 20-2000hz, the acceleration is 2-20g, the scanning period is 1 ~ 2 cycles, and it is necessary to stay near the resonance point for an additional period of time. The typical impact screening conditions are 1500-3000g and impact for 3 ~ 5 times. This test is only applicable to components.

Monitoring vibration and shock requires special test equipment, which is expensive and generally not used in civil electronic products.In addition to the above screening items, there are commonly used thickness leak detection, microscopic inspection, linear discrimination screening, precision screening, etc.

Screening criteria for common components:

Gjb548b-2005 test methods and procedures for microelectronic devices

Gjb7243-2011 technical requirements for screening military electronic components

QJ 10003-2008 screening guide for imported components

GJB 33a-1997 general specification for semiconductor discrete devices

GJB 63b-2001 general specification for solid electrolyte tantalum capacitors with reliability index

GJB 65B － 1999 general specification for electromagnetic relay with reliability index

GJB 597a-1996 general specification for semiconductor integrated circuits

Summary: electronic component testing runs through product design, component selection, component acceptance and selection in production stage, and product "secondary" screening in product delivery stage. Try to eliminate those defective or early failure devices caused by potential adverse factors such as raw materials, equipment, process and human factors from a batch of components, select qualified components with certain characteristics or judge whether the batch of products are qualified for acceptance, so as to improve the service reliability of products, especially for imported components, Through "secondary screening" to ensure controllable product quality and improve the overall reliability of equipment.